Did Germany attack Switzerland in WW2

Ok, since I think I finally got your real question (as I see it):

I'm simply asking if the defense of Switzerland during WW2 was overrated. Many people claim that the country was impossible to occupy, I just want to know if this is not clearly exaggerated.

The emphasis is what I interpret as your "real" question (since there is a lot of confusion here) and will answer it.

First of all, you probably have the wrong impression (partly). Switzerland never tried and was never seen as impossible to invade, even their well-planned defense wasn't impenetrable, and everyone knew that.

The only point was to make a possible invasion (and occupation) so lossy that it would never be worth it.

You got it right that the invasion would be over very quick, however, you go wrong with this one:

Feeding 800 000+ soldiers in the Alps for months if not years isn't realistic.

Because they were well prepared to hold out in their bunkers (and go raiding from there) for an extended amount of time.

And then we come to your "real" question (IMHO), which is not the invasion, but the occupation.

And that is where another of your questions comes in:

why would the German and Italian armies need to attack those strongholds in the mountains?

Because the Swiss planned to constantly attack out from these forts, waging a heavy and costly guerilla warfare from against the occupying troops.

This means Germany would have had two options: A) attack the forts, which would be time, supply and manpower-costly to no end. B) endure the terrorism

And B) would be costly. The French resistance could be dealt with (somewhat) because they were few, mostly untrained civilians with (mostly) scavenged equipment. And they did their part already. Now imagine that, but with 80k well trained, drilled, coordinated and fully equipped soldiers. Yeah, Germany would have pretty much a third front right in their backyard for years, which would have been unacceptable.

TLDR: Switzerland would have been hard (but possible) to invade, but almost impossible to occupy.